Field of the Invention
This application relates generally to intraocular lenses, and more specifically to stable intraocular lenses with reduced aberrant optical effects, such as reduced positive and/or negative dysphotopsia and increased field of view.
Description of the Related Art
A human eye can suffer diseases that impair a patient's vision. For instance, a cataract may increase the opacity of the natural crystalline lens, eventually resulting in blindness. To restore the patient's vision, the opaque lens may be surgically removed and replaced with an artificial intraocular lens, or IOL. An IOL may also be implanted to treat presbyopia or for other elective ocular surgical procedures. The IOL can be an accommodating IOL, which can adjust its axial position and/or shape to vary the optical power within a range in response to muscle action in the eye. As a result, the patient can focus on objects in a range of distances from the eye, rather than at one discrete distance. The IOL may also be a multifocal IOL utilizing a refractive and/or diffractive surfaces resulting in multiple focal points.
Healthy phakic eyes typically have a non-compromised visual field of about 60 degrees in the nasal direction, 105 degrees in the temporal direction, 65 degrees in the superior direction, and 70 degrees in the inferior direction. With current circular IOLs, pseudophakic eyes may have reduced field of view. Also, certain plate shaped IOLs have been found to have weak stability which may lead to displacement and/or rotation.
In addition, undesirable optical effects can arise after implantation of an IOL. One of the undesirable optical effects is dysphotopsia which is defined as the appearance of unwanted visible patterns. It is believed that light refracted into the IOL can reflect from a sharp or truncated edge of the IOL thereby causing glare, positive dysphotopsia, or other aberrant optical effects. Positive dysphotopsia can refer to the appearance of bright optical artifacts such as rings, halos, arcs or streaks. Negative dysphotopsia can refer to the appearance of dark shadows or lines in the field of vision. Negative dysphotopsia may occur when some light rays that enter the eye and are either (1) not incident on the IOL and pass by the IOL or (2) incident on the IOL edge, while immediately adjacent light rays enter the IOL and are refracted by and pass through the IOL onto the retina. Thus, stable IOLs that can reduce or mitigate aberrant optical effects, such as positive and/or negative dysphotopsia, as well as increase field of view are desirable.